Transportation networks may include a variety of field devices, with the field devices monitored and controlled to provide safe and reliable operation of the network. For example, field devices may be employed to detect one or more states or conditions of a transportation network, and/or to provide one or more states of operation. The information from one or more of the field devices may be provided to a central control system, which determines control actions for vehicles of the transportation networks using the provided information, and the central control system may provide control commands to one or more of the field devices to implement the control actions.
An interlocking may be employed to prevent conflicting vehicles from traversing the same portion of a route or track, to prevent a vehicle from passing over a switch or other device that is not properly set, or the like. The term “interlocking” may refer to a control scheme and/or control system that is configured to prevent one or more aspects of a transportation network from operating in a specified prohibited manner based on a condition or conditions of one or more other aspects of the transportation network. It may be noted that a portion of the transportation network associated with such a control scheme may also be referred to herein as an “interlocking.” Interlockings at crossings and/or junctions of transportation networks may be employed to prevent, for example, the granting of permission to enter a portion of the network or the display of a clear signal from one route when clearance has already been given to a conflicting vehicle, or if a conflicting vehicle is detected or determined as present on a conflicting route.
As one example, a vehicle transportation system may include tracks over which rail vehicles travel. These tracks may cross routes of other transportation systems, such as road or highway systems over which automobile traffic may pass. Further, tracks of different routes (and/or tracks forming sub-routes of a given route) may cross each other or be linked to allow for railroad crossings at grade (e.g., switches may allow a vehicle to transfer from one track or sub-route to a different track or sub-route). Wayside units may be disposed alongside tracks to monitor tracks for potential occupancy of tracks, to monitor the status of switches, to provide information and/or commands to rail vehicles in conjunction with Positive Train Control (PTC) systems, operate highway crossings, or the like.
Such interlockings may include discrete interfaces between controllers (e.g., solid state safety critical controllers) and field devices. Such discrete interfaces may connect at a terminal board. For maintenance purposes, the terminal board may contain an arrangement of test links such that the field devices may be disconnected from the controllers for the purpose of troubleshooting or testing the integrity of the cabling between the devices and the controllers without disarranging the connections between them. The test links may be employed by maintenance personnel when troubleshooting an interlocking. With a connection (or connections) between a controller and field devices broken, the maintenance personnel may then use a physical connection, such as jumper wires, to manually override the actual conditions of the field devices or controllers. As an example, maintenance personnel may apply voltages to the broken connections to bypass the voltages into or out of the controller. Such an approach allows for troubleshooting of an interlocking; however, such an approach is subject to safety concerns, for example safety issues caused by human error, inattention, or miscommunication.
For example, in the context of a rail transportation network, maintenance personnel may be troubleshooting a track switch that was intermittently reporting position of the switch to the controller. Such a condition, as properly designed, would not allow a dispatcher to clear the signal to allow train movement into the interlocking due to the intermittent reporting by the track switch. Maintenance personnel may use the test links to disconnect the track switch from the controller and to bypass the indication to the controller by applying jumper wires to the appropriate inputs of the controller. For example, such a bypass may be performed to attempt to determine if the issue with the intermittent reporting is in the controller, in the track switch, in the wiring from the track switch to the controller, or in the communication between the controller and the dispatcher.
However, if the dispatcher and the maintainer are not in detailed communication with each other, the track switch may appear to be properly indicating to the dispatcher, when in fact the indication to the dispatcher is the result of the bypass procedure. The dispatcher may then improperly clear the signal and allow a train to approach the interlocking. Thus, a train may traverse a track switch which was not aligned properly (e.g., for a given speed of the train), and the train may be derailed. Certain systems may provide for test modes for certain signaling equipment, for example to turn various lamps on within a signal head for cleaning, alignment, and adjustment; however, such testing procedures do not sufficiently address, for example, potential safety issues with troubleshooting switches or other mechanical components of a transportation network.